The rumen, the largest of the four stomach compartments of ruminants, is the site of digestive breakdown of ingested foodstuffs. Absorption of most nutrients for metabolic uptake by the animal, however, takes place further along in the alimentary tract, principally in the abomasum and intestines. Although the rumen endows the animal with the capacity to digest and utilize cellulose effectively, it is relatively inefficient in the digestion and utilization of dietary protein. Ingested food is retained in the rumen from between about 12 to 30 hours during which time it is subject to digestive breakdown by microbes and the rumen fluid. Protein and amino acids present in the diet are degraded and then become solubilized in the rumen liquid phase whereupon they are metabolized by the microbes as a convenient source of nutrition. Thus, most of the dietary protein and amino acids are diverted from the intended metabolic pathways of the ruminant.
In view of the inefficiency of protein conversion in ruminants, the supplementation of the ruminant diet with additional protein has become common practice. Supplemental protein is needed especially during periods of lactation and stress. To enhance efficiency, feed compositions have been modified to permit passage of the protein through the rumen in non-degraded, active form. Modifications have included coating the protein, e.g., with fats, fat or vegetable oils, polymers, or an acid sensitive coating; heat treatment; dispersing the active material in a polymeric matrix; and reacting the material with various compounds such as formaldehyde, acetylenic esters, polymerized unsaturated carboxylic acid or anhydrides, and phosphonitrilic halides. More specifically, U.S. Pat. No. 4,826,694 (McAskie) discloses a by-pass supplement wherein the proteinaceous feed additives are blended with a water-insoluble salt of one or more edible higher fatty acids. U.S. Pat. No. 4,533,557 (Maruyama et al.) discloses ruminant feed additives in the form of tablets or granules which contain a mixture of biologically active ingredients, chitosan and protective materials selected from saturated and unsaturated aliphatic fatty acids having from 14 to 22 carbon atoms, hardened vegetable oils and animal oils. Chitosan is disclosed as promoting the digestion of the active ingredient in the abomasum, while contributing resistance to degradation in the rumen.
U.S. Pat. No. 4,713,245 (Ando et al.) discloses granular ruminant feeds wherein a physiologically active substance is coated with an acid-sensitive substance and at least one other material selected from saturated and unsaturated fatty acids having at least 14 carbon atoms and salts thereof, animal or vegetable fats, and waxes, each having a melting point of at least 40.degree. C. Japanese Patent Laid-open 154956/1981 discloses a biologically effective granular substance coated with a mixture of saturated and unsaturated fatty acids having from 14-22 carbon atoms and salts thereof.
U.S. Pat. No. 3,959,493 (Baalsrud) discloses a rumen by-pass feed supplement comprising a biologically active material such as a carbohydrate, amino acid, fat or fatty acid, coated with or at least partly enclosed in a matrix of a rumen-resistant, saturated or unsaturated fatty acid having at least 14 carbon atoms, or a mixture thereof, or a salt of the acid or acid mixture. Baalsrud discloses feed supplements in which the fatty acid matrix consists entirely of saturated fatty acids, which would have limited bioavailability to the ruminant, and would instead provide a laxating effect, as well as feed supplements in which as much as one-half of the fatty acid matrix component is an unsaturated fatty acid, which would be too soft to form a commercially acceptable particle for feeding to a ruminant, such as a pellet, prill, and the like.
A need remains for a nutritionally efficient rumen by-pass feed supplement that is easily prepared on a large scale.